I imported an obj file into Blender and cannot add an uv wrap from a png file
To do this you must unwrap the .OBJ, (wavefront). You can do this by going to Edit Mode, selecting all of the faces by hitting 'A' on the keyboard, and pressing 'U' to unwrap. Then select unwrap or smart UV unwrap in the options drop down menu you get when hitting U, and you are done with the first step. The next step is to select a texture. By the way, you must be in Blender Cycles render mode to continue. Once you set your renderer to Cycles, go to the material settings for the object in the properties tab. Select whatever material you want for the object, and set the color to image texture. Then you can import your texture by clicking the file icon next to the image texture settings.